In manufacturing a semiconductor device, a metallization process is carried out for intra-device and inter-device electrical connections. This process gives great influence to the yield and reliability of a complicated integrated circuit of a sub-micron scale.
The conventional process of forming a metal contact portion of a semiconductor device is constituted as follows. An insulating layer is formed upon a semiconductor substrate on which a highly doped junction has been formed. Then the insulating layer is photo-etched to form a contact hole in such a manner so that a contact portion of the substrate (to which a metal layer is to be connected) is exposed. Then a metal contact portion is formed in such a manner so that the metal layer contacts the contact portion of the semiconductor substrate at the bottom of the contact hole.
FIGS. 1A-1C are partial sectional views showing the conventional process of forming a metal contact portion in a semiconductor device. Referring to these drawings, the conventional process of forming a metal contact portion of a semiconductor device will be described.
First, as shown in FIG. 1A, an insulating layer 13 is formed upon a semiconductor substrate 11 having a doped junction 12 formed thereon. Then a photoresist is spread on a surface of the insulating layer 13 to form a photoresist layer 14, and a contact portion is formed by performing a masking process.
As shown in FIG. 1B, by using the photoresist layer 14 as a mask, the insulating layer is etched so that the contact portion of the semiconductor device (to which the metal layer is to be connected) is exposed, thereby forming a contact hole 15.
Then the photoresist layer 14 is removed and then, as shown in FIG. 1C, a metal layer 16 is deposited on the entire surface thereof using a sputtering method, so that the metal layer contacts the contact portion of the substrate through the contact hole.
Thereafter, a metal wiring pattern is formed by carrying out a masking process and an etching process on the metal layer 16.
According to this conventional method, however, the size of the contact hole becomes very small for a semiconductor device which is governed by the sub-micron design rule, and therefore, the contact area between the metal and the semiconductor substrate becomes very small. As a result, the contact resistance is increased.